docs: further updates to PCPIntro(1) man page
docs: further updates to PCPIntro(1) man page

Add some notes about compund indoms that Marko was looking
for, and begin transitioning to introducing some consistency
in man pages as we discussed.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp